Brother MFC8420 Service Manual page 188

8) Remove the two cup S M3x6 Taptite screws, and then remove the NCU unit.
NCU unit
Taptite, cup S M3x6
9) Disconnect the heater harness and thermistor harness.
10) Remove the bind B M4x12 Taptite screw and the shoulder screw, and then remove the
fixing unit.
Shoulder screw
Heater harness
Taptite, bind B M4x12
Fig.5-18
Fixing unit
Fig.5-19
5-11
MFC-8420/8820D/8820DN, DCP-8020/8025D/8025DN
Thermistor harness
SERVICE MANUAL